Since the beginning of wire, and later wireless, communications, an implicit goal of communications systems has always been to bring remotely located participants as close together as possible. This is also the goal of a traditional teleconferencing system. Ideally, the effect obtained in good communications should be one of "being there."
A conventional teleconferencing system comprises two or more stations which are illustratively connected via the public switched telephone network. At each station, there is a camera for transmitting a video image to a remote station. There is also a microphone for picking up sound and forming an audio signal for transmission to the remote station. The typical teleconferencing station also includes a video monitor for receiving a video signal from the remote station to produce an image of a conferee at the remote station and a speaker for receiving an audio signal from the remote station.
In most teleconferencing systems, the video camera at a sending station is an NTSC camera which has a limited field of view. This camera forms an image on a conventional NTSC monitor at a receiving station remotely located relative to the sending station. One problem with this arrangement is that the conventional NTSC monitor is relatively small-sized. When the number of teleconference participants at the sending-end of a teleconference is larger than one, the image of each participant occupies a small portion of a small viewing area on the receiving monitor. As a result it becomes difficult for viewers at the receiving end of such an image to pick up non-verbal cues from the speaker's body and face. Indeed, in many cases it is often difficult to discern at the receiving-end who of the many participants at the sending-end is actually speaking.
U.S. Pat. No. 4,890,314, the contents of which are incorporated herein by reference, discloses a teleconferencing station which solves one aspect of this problem. In particular, in accordance with U.S. Pat. No. 4,890,314, a transmitting teleconferencing station includes, for example, first and second cameras which are specially arranged through the use of mirrors to have contiguous fields of view over a range of distances from the cameras. The two cameras produce first and second video signals corresponding to first and second sub-images. At the receiving teleconferencing station, the two sub-images are displayed using a display device so that the two sub-images merge contiguously to form a single high resolution image. The cameras at the transmitting station collectively have a larger field of view than a single camera would have, and, at the receiving-end, a much larger image is formed than would be the case if a conventional NTSC monitor were to be utilized.
A problem with this approach to forming a camera system with an aggregate wide area field of view is that there is a "seam" between the individual sub-images of the individual cameras when the individual sub-images are combined to form a single high resolution image. The seam appears because mirror edges are located just within the boundaries of the fields of view of the individual cameras.
In view of the foregoing, it is an object of the present invention to provide an arrangement of video cameras having individual fields of view which merge contiguously with one another to form an aggregate wide angle field of view and which produces a single high resolution image that does not exhibit a seam or other artifact at the boundary between the sub-images produced by the individual cameras.